The invention generally relates to aeration panels for introducing bubbles of gas, such as air, into a liquid body, including a tank of water, water basin, reservoir, or lake.
Conventional aeration panel structures having an upper portion consisting of a membrane mounted on a lower portion consisting of a flat, rigid plate are known, for example U.S. Pat. No. 5,192,467. Such structures have peripheral hold-down strips, which secure the membrane to the rigid plate. Middle hold-down strips are also provided to prevent billowing of the membrane. Adjustable anchor bolts hold the aeration panel structure to the bottom of a liquid container. Such panels are heavy, unwieldy when large, and difficult to transport and install. For this rigid plate approach, different materials, such as stainless steel or non-flexible plastic plates, are joined to flexible upper membrane sheets using screws, clamps or adhesives. Examples of other conventional aeration panel structures are also discussed in U.S. Pat. No. 5,192,467. Other aeration panel structures are also known, such as aeration panels described in German Patent Publication No. 29 42 697 and EP Patent Publication No. 0 229 386. Another example is U.S. Pat. Nos. 4,624,781, which describes a panel-type air diffusion device having an upper flexible membrane that is clamped to a lower rigid support plate. A further example is U.S. Pat. No. 5,015,421, which discloses a flexible membrane clamped to a rigid support with continuous clamping arrangements rather than point attachments, such as screws or rivets.
Still other aeration panels are known. For example, U.S. Pat. No. 6,406,005 discloses a rigid base plate and a perforated elastomeric membrane secured to the rigid base plate by sealing strips pressed along the edges of the membrane into corresponding grooves in the rigid base plate. Additionally, U.S. Pat. No. 5,532,391 describes a gas distributor including a base plate over which a perforated diaphragm is stretched and in which excessive expansion of the diaphragm is prevented by an upper grating. Furthermore, EP Publication No. 0 761 294 discloses an aerator panel with a perforated membrane secured to a support plate at the periphery and at central points on the panel while EP Publication No. 0 747 031 describes an anatomically shaped air bubble mat for use in a bathtub.
U.S. Pat. Nos. 6,558,549 and 6,645,374 teach a membrane module for gas transfer composed of a flexible oxygen-permeable membrane that is impermeable to liquid water. Because of the apparent absence of macroscopic perforations (instead alternative membranes are permissibly constructed of microporous hydrophobic materials), this apparatus does not produce bubbles in operation. Also, the apparatus is described as having a non-rigid restraint system and appears relatively flat.
All of the known aeration panels, especially the rigid support plate varieties, are heavy, expensive and difficult or unwieldy to install and maintain.